On 6 April 2012 07:21, Peter Eisentraut <pete...@gmx.net> wrote: > On lör, 2012-03-24 at 10:01 +0000, Gianni Ciolli wrote: >> ON (DELETE | UPDATE) actions for EACH foreign keys >> ================================================== >> >> ------------------ ----------- ----------- >> | ON | ON | >> Action | DELETE | UPDATE | >> ------------------ ----------- ----------- >> CASCADE | Row | Forbidden | >> SET NULL | Row | Row | >> SET DEFAULT | Row | Row | >> EACH CASCADE | Element | Element | >> EACH SET NULL | Element | Element | >> EACH SET DEFAULT | Forbidden | Forbidden | >> NO ACTION | - | - | >> RESTRICT | - | - | >> ------------------ --------- ------------- >> > I took another fresh look at this feature after not having looked for a > month or two. I think the functionality is probably OK, but I find the > interfaces somewhat poorly named. Consider, "PostgreSQL adds EACH > foreign keys" -- huh? I think they key word ELEMENT would be more > descriptive and precise, and it also leaves the door open to other kind > of non-atomic foreign key relationships outside of arrays. EACH has no > relationship with arrays. It might as well refer to each row. > > On the matter of the above chart, there has been a long back and forth > about whether the row or the element case should be the default. Both > cases are probably useful, but unfortunately you have now settled on > making maximum destruction the default. Additionally, we would now have > the case that sometimes, depending on some configuration elsewhere, an > ON DELETE CASCADE deletes more than what was actually involved in the > foreign key. What I'd suggest is to make both cases explicit. That is, > forbid ON DELETE CASCADE altogether and make people write ON DELETE > CASCADE ROW or ON DELETE CASCADE ELEMENT. In addition to making things > more explicit and safer, it would again leave the door open to other > kinds of relationships later.
+1 -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
